High-frequency transmitter



July 25, 1939. H. HORNUNG l 2,167,511

HIGH-FREQUENCY TRANSMITTER Filed April 23, 1935 Patented July 25, 1939 UNITED STATES HIGH-FREQUENCY TRANSMITTER Heinrich Hornung, Berlin-Tempelhof, Germany,

assignor to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof, Germany, a company Application April 23, 1935, Serial No. 17,806 In Germany May 3, 1934 3 Claims.

The invention relates to high frequency transmitters of the kind adapted to work with a variable wave range, and it has for its object to effect that the transmitted amplitudes be of the same amplitude, or nearly so, independently of the frequency on which the arrangement be operating at the time being.

One embodiment of the invention is shown in the accompanying drawing in which Fig. 1 is a diagrammatic representation of a transmitting arrangement constructed according to the invention, Fig. 2 shows the resonance curve of a transformer provided in this arrangement, Fig. 3 shows diagrammatically the application of the control arrangement to more than one preamplier stage.

In Fig. 1 two stages of a high frequency transmitter are represented. The two valve-tubes are designated RI and R2. The anode circuit of the 20 tube Rl is connected with the grid circuit of the tube R2 through a transformer K which contrarily to the transformers hitherto known is provided with an iron core. The iron here employed may be the high frequency iron which has recently become known and contains nely 25 divided iron powder. Transformers of this kind have a pretty well marked resonance curve a, as will be seen from Fig. 2. It is of course to be considered in this respect that the frequency range is much greater than in the case of low 30 frequency transformers, these being usually the devices for which resonance curves of this kind are plotted. Over a broad range of wave lengths the variable transmission effected by the coupling transformer would result in amplitudes which are 35 different for different frequenci-es. The means which in such cases are used in the low frequency art, such as attenuation resistances and the like, cannot be employed with transmitters since here on account of heating effects the operation must entail as little losses as possible.

It is proposed by the invention to control the grid bias of one or several prestages in dependency upon the grid current of the transformercoupled stage. For this purpose a resistance WI 45 is connected in series with the secondary of the transformer K, Fig. 1, a grid control voltage for the tube RI being derived from this resistance. This voltage is applied over a resistance W2 to the grid of the tube RI. In dependency upon the resonance curve a of Fig. 2, of the transformer, a grid current arises in the grid circuit of the tube R2, that is to say, if the voltage amplitude in the grid circuit of the tube R2 increases then the grid current will increase. This variation of the grid 55 current is led as a voltage variation to the grid bias of the tube RI and the relationships are so elected that a frequency curve b is Obtained which is as rectilinear as possible,

(Cl. Z50-17) This idea may be employed not only for the prestage as shown in the example represented in the drawing, but may be used also for regulating another prestage, such as the rst stage of a three-stage arrangement, or for regulating two prestages at the same time. Such an arrangement is illustrated in Fig. 3. The regulating potential derived from the final stage E is simultaneously applied to the amplifying stages V1 and V2 in a manner similar to that illustrated in Fig. l so that a change in the grid bias is simultaneously effected in these preamplication stages. It is immaterial also how the regulation is effected. All the amplitude-regulating devices that have become known may be employed here in principle, just as used also for fading-compensation and the like.

What is claimed is:

1. A high frequency transmitter adapted to operate over a variable frequency range for transmitting selectively any wave in said range comprising a plurality of amplifying stages connected in cascade, each stage including a Vacuum tube having cathode, grid and anode, an iron core transformer coupling one of said stages to a succeeding stage thereof, said transformer having an amplitude characteristic varying with frequency, and means for compensating said Varying characteristic comprising means controlled by the grid current of a tube in a stage coupled to the secondary of said transformer for controlling the grid bias of the tubes of said preceding stages whereby the output of said transmitter is maintained substantially constant over said frequency range.

2. A high frequency transmitter adapted to operate over a variable frequency range for selectively transmitting any frequency in said range comprising a plurality of amplifying stages connected in cascade, each stage including a vacuum tube having a cathode, a grid and an anode, an iron core transformer coupling one of said stages to a succeeding stage thereof, said transformer having an amplitude characteristic varying with frequency, said circuit being so arranged as to insure a grid current in a stage coupled to the secondary of said transformer and means to compensate for said varying amplitude characteristic, comprising means controlled by the grid current of the tube in said stage last mentioned for controlling the grid bias of a tube in one of the stages preceding said transformer whereby the amplitude of the output of said transmitter is maintained substantially constant for all frequencies in said frequency range.

3. A high frequency transmitter in accordance with claim 2, in which the iron core of said coupling transformer comprises a finely divided mag- Iltic iron powder.

HEINRICH HORNUNG. 

